284 CYTOLOGiCAL METHODS. 



or with dilute glycerin (Calberla's formula would be a good 

 one in many cases). For further details see ante, 52. 



Sulphurous acid has been used by CAENOY (La Cellule, i, 1885, p. 212 ; 

 ii, 1886, p. 17) and by GILSON (ibid., ii, 1886, p. 84). It is prepared for 

 use by saturating cold absolute alcohol with well-dried S(X. It may be used 

 in the ordinary way, or by exposing the objects for a few seconds to the 

 vapours of the solution. It kills rapidly, but only fixes the chromatin, and 

 is therefore not likely to be generally useful. 



Uranium Salts are mild fixing agents, and very penetrating, and may 

 be useful for some special objects (see 65). 



Lemon Juice (fresh, filtered) has lately been warmly recom- 

 mended as a fixative for nuclei by van G-EHUCHTEN (Anat. 

 Anzeig.j iv, 1889, p. 52). Fix for five minutes, wash well with 

 water and stain with methyl green, and examine in liquid of 

 Ripart and Petit. 



604. Cytological Stains. For fresh or lightly fixed tissues 

 methyl green is the most generally useful nuclear stain. For 

 the properties of this reagent see ante, 105. 



Bismarck brown is another useful stain for such objects. 

 It may be used in aqueous solution with acetic acid or with 

 hydrate of chloral, or dissolved in dilute glycerin. Alum- 

 carmine may occasionally be useful. Delafield's haematoxylin 

 will render services for osmium objects. Methyl violet, em- 

 ployed according to the method of GEASEE ( 107), may also 

 be found a very useful stain. 



For sections of hardened tissues, the best chromatin stains 

 are those obtained by means of safranin, gentian violet, 

 Victoriablau, and some other anilins, used according to the 

 indirect or Fleinming's method. This has been so fully ex- 

 plained in Chapter VIII that it is only necessary to refer the 

 reader back to the paragraphs in question. 



BABES'S supersaturated safranin stain (Arch. f. mik. Anat., 

 xxii, 1883, p. 361) may also occasionally be useful. It is as 

 follows : A supersaturated solution of safranin in water is 

 warmed to 60 C., and filtered warm. On cooling, it becomes 

 turbid through the formation of small crystals. Sections are 

 placed in a watch-glass with some of this turbid solution, and 

 the whole is warmed for a few seconds (till the liquid becomes 

 clear) over a spirit-lamp. Allow the whole to remain for one 

 minute, and wash out with water, and treat with alcohol and 

 turpentine in the ususl way. Tissues which do not take on 



